Kite Pharma's (KITE) disclosed Tuesday six-month results from a pivotal study of its CAR-T therapy in patients with aggressive lymphomas that showed only a slight degradation in response rates and no new safety concerns compared to results previously seen at three months.

After six months, about one-third of lymphoma patients treated with Kite's KTE-C19 had a complete response, meaning all evidence of their tumors disappeared. The response to KTE-C19 is impressive because these patients entered Kite's study with cancer no longer responsive to all previous treatments.

CAR-T, or chimeric antigen receptor T-cells, is a new form of cancer immunotherapy in which a patient's own T cells are removed and then engineered to identify and kill malignant blood cancer cells.

Kite intends to submit a marketing application for KTE-C19 to the U.S. Food and Drug Administration by the end of March. A similar application for Europe will also be submitted this year, the company said.

Kite shares were halted Tuesday morning at $56.83.

In the pivotal study, 77 patients with advanced diffuse large B-cell lymphoma (DLBCL) were treated with Kite's KTE-C19. The complete response rate at six months was 31%. That compares to a complete response rate of 33% at three months.

The study also enrolled another 24 patients with two other forms of aggressive lymphomas. Combined, the 101 patients in the study had a 36% complete response rate after six months of follow up.

The durability of response to KTE-C19 came with no additional safety issues. There were no new patient deaths from adverse events at the six month follow up beyond the three patient deaths previously disclosed by Kite last year.

The rate of serious cytokine release syndrome, a well-known and potentially fatal toxicity associated with CAR-T, fell to 13% at six months from 18% at three months. There were no cases of cerebral edema reported in the study, Kite said.

Kite is competing against Novartis (NVS) - Get Report and Juno Therapeutics (JUNO) in the race to develop and approve CAR-T therapies for patients with various types of blood cancers. Novartis is also expected to seek regulatory approval for its CAR-T therapy this year.

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